cold starts are 500ms on average, and that's only for the first call that wakes up the db from hibernation. people still seem to think that this latency happens for every call (see other threads here) but once the service has woken up (cold start over) you're back to regular (sub 10ms) latency timings and the service continues to run that way. you'll only hit a cold start again if (you have this option turned on) your service goes idle for > 5 min. You can turn scale-to-zero off and you'll run 24/7, have zero cold starts.
$19 plan is going away, will launch a better $5 plan soon.